Granulocytic ehrlichiosis occurs in mammals and is caused by infection of granulocytic cells with the tick-borne agent E. ewingii. Frequently reported symptoms of granulocytic ehrlichiosis in humans are anemia and thrombocytopenia. Common clinical signs in dogs are fever and lameness.
Indirect immunofluorescence assays (IFA) and enzyme-linked immunosorbent assays (ELISA) are frequently used as aids in the diagnosis of diseases caused by E. ewingii by measuring the binding of antibody from a patient's blood or serum to infected cells, cell lysates or purified Ehrlichial proteins. Commonly, these tests are made using Ehrlichia species other than E. ewingii (for example E. canis or E. chaffeensis) as surrogate markers because E. ewingii-specific reagents are not easily grown in tissue culture and, therefore, have heretofore been unavailable for, e.g., Immuno-Fluorescence Assays (IFA). Assays using surrogate markers are severely limited in usefulness because of sensitivity and specificity issues directly related to the impure nature and the non-specific nature of the antigen or antigens used in these tests. Highly purified reagents are needed to construct more accurate assays. This invention discloses specific synthetic peptide sequences derived from E. ewingii that can be used in place of purified proteins, partially purified proteins, infected cells, or cell lysates from Ehrlichia species other than E. ewingii. 